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GLOBAL WIND PATTERNS
The most common wind direction is called the prevailing winds.
When Columbus set sail for Asia (and
“discovered” the Americas) he utilized the
prevailing winds. He knew that at about 20°
north latitude he would find dependable
winds from the north-east which would carry
his ships quickly westward across the Atlantic
Ocean. On his return, he sailed northward to
the zone of prevailing westerlies, that ferried
him back to Europe. (See the diagram below.)
These wind belts soon became the avenues of
the triangular trade routes. Merchants from
England sent manufactured items to Africa,
where they were traded for negro slaves.
The slaves were sailed across the Atlantic on
the north-east trade winds. In the Americas,
the
slaves were traded for rum and cotton, which
were
shipped to England on the prevailing westerlies farther to the north. The rum and cotton were sold
in England for a considerable profit to the owners and investors. The north-east trade winds and
the mid-latitude westerlies are two zones of the world wide pattern of prevailing winds.
1. Why did Columbus sail south along Africa before he sailed west to the Americas?
2. What do we call winds from the most common wind direction?
3. Winds are heat flow by
.
If the Earth were not in
motion, the world wide pattern
of winds would be very simple.
As this diagram shows, we
would have two giant
convection cells. Warm, moist
air would rise at the equator
and travel toward the poles. At
the poles, the air would cool,
sink, and blow south to the
equator. But the Earth is
moving; it rotates. Therefore,
the Coriolis force makes the
actual pattern more complex.
Global Wind Patterns, page 1 of 4
This diagram shows the true
pattern of Earth’s prevailing
winds.
Notice how the winds curve to
the right in the northern
hemisphere and to the left in
the southern hemisphere.
4. In the Bay Area, the
prevailing winds come from
the
Notice how the winds in the
southern hemisphere are a
mirror reflection of the
northern hemisphere winds.
Most of the wind belt names are easy to understand, but the doldrums may be unfamiliar. The
doldrums are the regions of weak and undependable winds near the equator, where warm moist air
is often rising.
5. According to the map above, near the poles, the winds usually blow from the
6. Winds always blow from
because of the
pressure toward
pressure, and they curve
effect.
Vertical
profiles of
Earth’s
atmosphere
from the North
Pole to the
South Pole.
7. Along the equator, the air movies mostly along the Earth, or up higher into the atmosphere.
(Circle one choice)
8. Why is the climate often wet near the equator?
Global Wind Patterns, page 2 of 4